A Levey-Jennings chart plots the results of multiple measurements of a single control sample over time, with the mean and standard deviation of the measurements calculated at each time point. The control sample is a material of known concentration or value that is analyzed alongside patient samples to ensure the accuracy and precision of the test.

Levey-Jennings charts are widely used in medical laboratories and are a key component of quality assurance programs. They are also used in other industries, such as food manufacturing and environmental testing, to monitor the performance of analytical methods and ensure the accuracy and reliability of test results.